Plasma processing method and apparatus

ABSTRACT

A plasma processing method includes exhausting the interior of a vacuum chamber while supplying gas into the vacuum chamber while maintaining the interior of the vacuum chamber at a desired pressure. A high-frequency power of 100 kHz to 100 MHz is applied to a coil provided in the vicinity of a dielectric window which faces a substrate placed on a substrate electrode in the vacuum. Plasma is generated in the vacuum chamber to process the substrate or a film on the substrate. Particles which tend to move straight from a surface of the substrate or from a surface of the film on the substrate toward a wall surface of the dielectric window inside the vacuum chamber are kept interrupted by a metal plate.

This is a divisional application of U.S. patent application Ser. No.10/114,238, filed Apr. 3, 2002, now allowed.

BACKGROUND OF THE PRESENT INVENTION

The present invention relates to a plasma processing method andapparatus, such as an etching method and apparatus, to be used formanufacture of semiconductors or other electron equipment andmicromachines.

For manufacture of semiconductors or other electron equipment andmicromachines, demands for etching techniques related to refractorymetal films have been increasing year after year.

For example, in the field of semiconductor memories (storage devices),although countermeasures for increases in the capacitance of memorycapacitors have hitherto been given by changing the memory capacitorstructure, it has become difficult to secure demanded capacitances onlyby the structure change with progress of miniaturizing. Due to this,ceramic base oxides having high dielectric constants such asbarium/strontium titanate, lead zirconium titanate, andbismuth/strontium tantalate have come to be used as materials forcapacitor capacitance. Since elimination of oxygen from these ceramicbase oxides would cause their characteristics to largely deteriorate,such materials exhibiting low reaction with oxygen as ruthenium,platinum, iridium, and rhodium are used as materials for capacitorelectrodes. Forming microfine patterns by using these materials requiresetching techniques for those materials.

Moreover, not only for Si-based semiconductors but also for compoundsemiconductors, there has arisen a need for an etching process in whichcontact holes are formed in an insulator film with a refractory metalfilm used as an undercoat film. In this case, although the insulatorfilm is targeted for the etching, the refractory metal, which is theundercoat film, also would be etched to some extent in overetching.

An etching using an inductively coupled plasma source as an example ofthe prior-art etching method is explained below with reference to FIG.7. Referring to FIG. 7, while a vacuum chamber 1 is maintained at aspecified internal pressure by exhausting the vacuum chamber 1 with aturbo-molecular pump 3 serving as an exhauster and simultaneouslysupplying a specified gas from gas supply equipment 2 into the vacuumchamber 1, a high-frequency power of 13.56 MHz is supplied to a coil 6provided on a dielectric plate 20 by means of a coil-use high-frequencypower supply 4, by which plasma is generated in the vacuum chamber 1,allowing the etching on a substrate 8 placed on a substrate electrode 7to be achieved. Further, a substrate-electrode use high-frequency powersupply 9 for supplying a high-frequency power of 400 kHz to thesubstrate electrode 7 is provided, allowing ion energy reaching thesubstrate 8 to be controlled.

The turbo-molecular pump 3 and an exhaust port 10 are disposed justunder the substrate electrode 7, and a pressure-controlling valve 11 formaintaining the vacuum chamber 1 at the specified pressure is an up-downvalve located just under the substrate electrode 7 and just over theturbo-molecular pump 3.

With an etching apparatus having such a constitution, an iridium filmcan be etched under the conditions of an Ar/Cl₂ of 260/20 sccm, apressure of 0.3 Pa, and an ICP (coil power)/BIAS (substrate-electrodepower) of 1500/400 W.

Further, a silicon oxide film on a gold film can be etched under theconditions of an Ar/CHF₃ of 270/30 sccm, a pressure of 2.5 Pa, and anICP/BIAS of 1500/600 W.

However, in the etching of iridium described in the prior art example,which consists mainly of physical etching, an electrically conductiveiridium thin film would deposit on the surface of the dielectric plate20. Therefore, a high-frequency electromagnetic field generated in thevacuum chamber 1 as a result of supplying high-frequency power to thecoil 6 would be gradually weakened, and a decline of the etching ratewould occur as an issue as shown in FIG. 8.

Also, in the etching of a silicon oxide film described in the prior artexample, in which gold forming an undercoat film would be etched to someextent in overetching, where the etching of gold also consists mainly ofphysical etching, an electrically conductive gold thin film would bedeposited on the surface of the dielectric plate 20. Therefore, ahigh-frequency electromagnetic field generated in the vacuum chamber 1as a result of supplying high-frequency power to the coil 6 would begradually weakened, and a decline of the etching rate would occur as anissue as shown in FIG. 9.

SUMMARY OF THE PRESENT INVENTION

Having been accomplished in view of these and other prior-art issues, anobject of the present invention is to provide a plasma processing methodand apparatus capable of achieving uniform plasma processing andensuring a stable etching rate.

In accomplishing these and other aspects, according to a first aspect ofthe present invention, there is provided a plasma processing methodcomprising: exhausting the interior of a vacuum chamber while supplyinggas into the vacuum chamber; and, while maintaining the interior of thevacuum chamber at a pressure, applying a high-frequency power of 100 kHzto 100 MHz to a coil provided in a vicinity of a dielectric windowprovided so as to face a substrate placed on a substrate electrode inthe vacuum chamber. Thus, plasma is generated in the vacuum chamber toprocess the substrate or a film on the substrate by the generated plasmawhile particles which tend to move straight from a surface of thesubstrate or from a surface of the film on the substrate toward a wallsurface of the dielectric window inside the vacuum chamber areinterrupted (blocked) by a metal plate.

According to a second aspect of the present invention, there is provideda plasma processing method according to the first aspect, wherein whenthe plasma is generated inside the vacuum chamber, the high-frequencypower of 100 kHz to 100 MHz is applied to the coil provided inside adielectric cylinder serving as the dielectric window and outside avacuum chamber.

According to a third aspect of the present invention, there is provideda plasma processing method according to the first or second aspect,wherein the plasma processing is a process of etching the substrate orthe film on the substrate.

According to a fourth aspect of the present invention, there is provideda plasma processing method according to the first or second aspect,wherein the plasma processing is a process of etching a refractory metalfilm on the substrate.

According to a fifth aspect of the present invention, there is provideda plasma processing method according to the first or second aspect,wherein the plasma processing is a process of etching a thin film formedon a refractory metal film on the substrate.

According to a sixth aspect of the present invention, there is provideda plasma processing method according to the fourth or fifth aspect,wherein the refractory metal film is a film containing at least oneelement of iridium, rhodium, ruthenium, platinum, gold, copper, rhenium,bismuth, strontium, barium, zirconium, lead, and niobium.

According to a seventh aspect of the present invention, there isprovided a plasma processing method according to the second aspect,wherein the high-frequency power of 100 kHz to 100 MHz is applied to thecoil provided outside the vacuum chamber on a dielectric cylinderserving as the dielectric window in a state in which a first metal plateprovided at a bottom portion of the dielectric cylinder inside thevacuum chamber is connected to a second metal plate provided at an upperportion of the dielectric cylinder on its side opposite to the bottomportion inside the vacuum chamber by means of a metal rod or boltextending through a penetration hole provided along an axis of thedielectric cylinder while the dielectric cylinder is fixed by beingsandwiched between the first metal plate and the second metal plate.

According to an eighth aspect of the present invention, there isprovided a plasma processing method according to the second aspect,wherein the high-frequency power of 100 kHz to 100 MHz is applied to thecoil provided outside the vacuum chamber on a dielectric cylinderserving as the dielectric window in a state in which a first metal plateprovided at a bottom portion of the dielectric cylinder inside thevacuum chamber is connected to a second metal plate provided at an upperportion of the dielectric cylinder on its side opposite to the bottomportion inside the vacuum chamber by means of a metal fastener such as arod or bolt disposed outside the vacuum chamber on the dielectriccylinder while the dielectric cylinder is fixed by being sandwichedbetween the first metal plate and the second metal plate.

According to a ninth aspect of the present invention, there is provideda plasma processing method according to the seventh or eighth aspect,wherein the metal rod or bolt, the first metal plate, and the secondmetal plate are at a ground potential.

According to a 10th aspect of the present invention, there is provided aplasma processing method according to the seventh or eighth aspect,wherein the processing is carried out in a state in which a line segmentinterconnecting an arbitrary point on a vacuum-side wall surface of thedielectric cylinder and an arbitrary point on a surface of the substrateis interrupted by the first metal plate provided at the bottom of thedielectric cylinder.

According to an 11th aspect of the present invention, there is provideda plasma processing method according to the seventh or eighth aspect,wherein a diameter of the first metal plate is 1 to 1.5 times largerthan a diameter of the substrate electrode, and a diameter of the secondmetal plate is 1.6 to 3 times larger than a diameter of the substrateelectrode.

According to a 12th aspect of the present invention, there is provided aplasma processing method according to the seventh or eighth aspect,wherein a distance between the first metal plate and the substrateelectrode is 40 mm to 150 mm.

According to a 13th aspect of the present invention, there is provided aplasma processing method according to the first or second aspect,wherein the vacuum chamber has a pressure not more than 10 Pa.

According to a 14th aspect of the present invention, there is provided aplasma processing method according to the first or second aspect,wherein the vacuum chamber has a pressure not more than 3 Pa.

According to a 15th aspect of the present invention, there is provided aplasma processing apparatus comprising: a vacuum chamber; gas supplyequipment for supplying gas into the vacuum chamber; exhaust equipmentfor exhausting the vacuum chamber; a pressure-controlling valve formaintaining the vacuum chamber at an internal pressure; a substrateelectrode for placing thereon a substrate in the vacuum chamber; adielectric window provided so as to face the substrate electrode; a coilprovided in a vicinity of the di electric window; and high-frequencypower supply equipment capable of supplying high-frequency power of 100kHz to 100 MHz to the coil. A line segment interconnecting an arbitrarypoint on a vacuum-side wall surface of the dielectric window and anarbitrary point on a surface of the substrate is interrupted by a metalplate.

According to a 16th aspect of the present invention, there is provided aplasma processing apparatus comprising: a vacuum chamber; gas supplyequipment for supplying gas into the vacuum chamber; exhaust equipmentfor exhausting the vacuum chamber; a pressure-controlling valve formaintaining the vacuum chamber at an internal pressure; a substrateelectrode for placing thereon a substrate in the vacuum chamber; adielectric cylinder provided so as to face the substrate electrode; acoil provided inside the dielectric cylinder and outside the vacuumchamber; and high-frequency power supply equipment capable of supplyinghigh-frequency power of 100 kHz to 100 MHz to the coil.

According to a 17th aspect of the present invention, there is provided aplasma processing apparatus according to the 16th aspect, furthercomprising: a first metal plate provided at a first-side bottom of thedielectric cylinder facing the substrate electrode; and a second metalplate provided at the other (second) side bottom of the dielectriccylinder not facing the substrate electrode. The first metal plate isconnected to the second metal plate by means of a metal rod or a boltextending through a penetration hole provided along a cylinder axis ofthe dielectric cylinder while the dielectric cylinder is fixed by beingsandwiched between the first metal plate and the second metal plate.

According to an 18th aspect of the present invention, there is provideda plasma processing apparatus according to the 16th aspect, furthercomprising: a first metal plate provided at a one-side bottom of thedielectric cylinder facing the substrate electrode; and a second metalplate provided at the other side bottom of the dielectric cylinder notfacing the substrate electrode. The first metal plate is connected tothe second metal plate by means of a metal rod or a bolt providedthrough a space inside the dielectric cylinder while the dielectriccylinder is fixed by being sandwiched between the first metal plate andthe second metal plate.

According to a 19th aspect of the present invention, there is provided aplasma processing apparatus according to the 17th or 18th aspect,wherein the metal rod or bolt, the first metal plate, and the secondmetal plate are at a ground potential.

According to a 20th aspect of the present invention, there is provided aplasma processing apparatus according to the 17th or 18th aspect,wherein a line segment interconnecting an arbitrary point on avacuum-side wall surface of the dielectric cylinder and an arbitrarypoint on a surface of the substrate is interrupted by the first metalplate provided at the bottom of the dielectric cylinder.

According to a 21st aspect of the present invention, there is provided aplasma processing apparatus according to the 17th or 18th aspect,wherein a diameter of the first metal plate is 1 to 1.5 times largerthan a diameter of the substrate electrode and a diameter of the secondmetal plate is 1.6 to 3 times larger than a diameter of the substrateelectrode.

According to a 22nd aspect of the present invention, there is provided aplasma processing apparatus according to the 17th or 18th aspect,wherein a distance between the first metal plate and the substrateelectrode is 40 mm to 150 mm.

According to a 23rd aspect of the present invention, there is providedan etching method comprising: maintaining the interior of a vacuumchamber at a pressure by exhausting the vacuum chamber while supplyinggas into the vacuum chamber; and applying a high-frequency power of 100kHz to 100 MHz to a coil provided inside a dielectric cylinder andoutside the vacuum chamber provided so as to face a substrate placed ona substrate electrode in the vacuum chamber, thus generating plasma inthe vacuum chamber so as to etch a refractory metal film on thesubstrate.

According to a 24th aspect of the present invention, there is providedan etching method comprising: maintaining the interior of a vacuumchamber at a pressure by exhausting the vacuum chamber while supplyinggas into the vacuum chamber; and applying a high-frequency power of 100kHz to 100 MHz to a coil provided inside a dielectric cylinder andoutside the vacuum chamber provided so as to face a substrate placed ona substrate electrode in the vacuum chamber, thus generating plasma inthe vacuum chamber so as to etch a thin film formed on a refractorymetal film on the substrate.

According to a 25th aspect of the present invention, there is providedan etching method according to the 23rd or 24th aspect, wherein therefractory metal film is a film containing at least one element ofiridium, rhodium, ruthenium, platinum, gold, copper, rhenium, bismuth,strontium, barium, zirconium, lead, and niobium.

According to a 26th aspect of the present invention, there is providedan etching method according to the 23rd or 24th aspect, wherein theetching is carried out in a state in which a first metal plate providedat a first-side bottom of the dielectric cylinder facing the substrateelectrode is connected to a second metal plate provided at the other(second) side bottom of the dielectric cylinder not facing the substrateelectrode. The connection of the first metal plate to the second metalplate is by a metal rod or a bolt extending through a penetration holeprovided along a cylinder axis of the dielectric cylinder while thedielectric cylinder is fixed by being sandwiched between the first metalplate and the second metal plate.

According to a 27th aspect of the present invention, there is providedan etching method according to the 23rd or 24th aspect, wherein theetching is carried out in a state in which a first metal plate providedat a first-side bottom of the dielectric cylinder facing the substrateelectrode is connected to a second metal plate provided at the other(second) side bottom of the dielectric cylinder not facing the substrateelectrode. The connection of the first metal plate to the second metalplate is by a metal rod or a bolt provided in a space inside thedielectric cylinder while the dielectric cylinder is fixed by beingsandwiched between the first metal plate and the second metal plate.

According to a 28th aspect of the present invention, there is providedan etching method according to the 26th or 27th aspect, wherein themetal rod or bolt, the first metal plate, and the second metal plate areat a ground potential.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1 is a sectional view showing the constitution of an etchingapparatus used in a first embodiment of the present invention;

FIG. 2 is an enlarged and partially sectional view showing theconstitution of the etching apparatus used in the first embodiment ofthe present invention;

FIG. 3 is a graph showing variations in the etching rate in the firstembodiment of the present invention;

FIG. 4 is a sectional view showing the constitution of an etchingapparatus used in a second embodiment of the present invention;

FIG. 5 is an enlarged and partially sectional view showing theconstitution of the etching apparatus used in the second embodiment ofthe present invention;

FIG. 6 is a graph showing variations in the etching rate in the secondembodiment of the present invention;

FIG. 7 is a sectional view showing the constitution of an etchingapparatus used in the prior art example;

FIG. 8 is a graph showing variations in the etching rate in the priorart example;

FIG. 9 is a graph showing variations in the etching rate in anotherprior art example;

FIG. 10 is a plan view of the etching apparatus of FIG. 1; and

FIG. 11 is an enlarged and partially sectional view showing theconstitution of an etching apparatus used in a third embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout the accompanying drawings.

Hereinbelow, a first embodiment of the present invention is describedwith reference to FIGS. 1 to 3 and 10.

FIG. 1 shows a sectional view of an etching apparatus as an example of aplasma processing apparatus used in a first embodiment of the presentinvention. Referring to FIG. 1, while a vacuum chamber 1 is maintainedat a specified internal pressure by exhausting the vacuum chamber 1 witha turbo-molecular pump 3 serving as an exhauster and simultaneouslysupplying a specified gas from nozzles 2A of gas supply equipment 2 intothe vacuum chamber 1, a high-frequency power of 13.56 MHz is supplied bymeans of a coil-less high-frequency power supply 4 to a coil 6 providedinside a dielectric cylinder 5 which serves as one example of adielectric window and is formed of glass or ceramics, such as quartzglass, alumina, aluminum nitride or silicon nitride (SiN₄). Thus, plasmais generated in the vacuum chamber 1, allowing the etching on an objectsuch as a substrate 8 or a thin film thereon placed on a substrateelectrode 7 to be performed. Further, a substrate-electrode useshigh-frequency power supply equipment 9 for supplying high-frequencypower of 400 kHz to the substrate electrode 7 is provided, allowing ionenergy reaching the substrate 8 to be controlled. Examples of the thinfilms on the substrate 8 are a silicon oxide film, a silicon nitridefilm, etc.

The turbo-molecular pump 3 and an exhaust port 10 are disposed justunder the substrate electrode 7, and a pressure-controlling valve 11 formaintaining the vacuum chamber 1 at the specified pressure is an up-downvalve located just under the substrate electrode 7 and just over theturbo-molecular pump 3. Thus, the pressure-controlling valve 11 moves upand down to control the pressure in the vacuum chamber 1 to set thepressure at a specified pressure. A first solid metal plate 12 made ofaluminum and having an alumite-coated surface, for example, is providedat a first-side bottom of the dielectric cylinder 5 facing the substrateelectrode 7, and a second metal plate 13 made of aluminum and having analumite-coated surface for example is provided at the other (second)side of the dielectric cylinder 5 not facing the substrate electrode 7.The first metal plate 12 is connected to the second metal plate 13 by aplurality bolts 15 made of stainless steel for example and extendingthrough penetration holes 14 provided in the dielectric cylinder 5 alongthe cylinder axis of the dielectric cylinder 5. The dielectric cylinder5 is fixed by being sandwiched between the first metal plate 12 and thesecond metal plate 13. That is, as shown in FIG. 2, the dielectriccylinder 5 is located on the outer edge surface of the first metal plate12, and the outer edge of the first metal plate 12 and the inner edge ofthe dielectric cylinder 5 is located on the inner edge of the secondmetal plate 13 while the bolts 15 are connected between the first metalplate 12 and the second metal plate 13 through the dielectric cylinder5. The bolts 15, the first metal plate 12, and the second metal plate 13are at the ground potential.

Also, as shown in FIG. 2, a straight line segment interconnecting anarbitrary point A on the vacuum-side wall surface of the dielectriccylinder 5 and an arbitrary point B on the substrate surface isinterrupted (intersected) by the first metal plate 12 provided at thebottom of the dielectric cylinder 5. That is, when plasma processing iscarried out, particles which tend to move straight from a surface of thesubstrate 8 or from a surface of the film on the substrate 8 toward awall surface of the dielectric cylinder 5 inside the vacuum chamber 1through the plasma processing are interrupted (blocked) by the firstmetal plate 12, thus preventing deposition of a thin film on thedielectric cylinder 5.

With the etching apparatus having such a constitution, an iridium filmwas etched under the conditions of an Ar/Cl₂ of 260/20 sccm, a pressureof 0.3 Pa, and an ICP (coil power)/BIAS (substrate-electrode power) of1500/400 W. A transition of etching rate is shown in FIG. 3. As apparentfrom FIG. 3, such declines of etching rate as seen in the prior artexample have been eliminated.

The reason why a stable etching rate has been ensured as shown above canbe that the iridium thin film is no longer deposited on the surface ofthe dielectric cylinder 5 so that the high-frequency electromagneticfield generated in the vacuum chamber 1 as a result of supplying thehigh-frequency power to the coil 6 has become stable in strength.

Next, a second embodiment of the present invention is described withreference to FIGS. 4 to 6.

FIG. 4 shows a sectional view of an etching apparatus used in the secondembodiment of the present invention. Referring to FIG. 4, while a vacuumchamber 1 is maintained at a specified internal pressure by exhaustingthe vacuum chamber 1 with a turbo-molecular pump 3 serving as anexhauster and simultaneously supplying a specified gas from gas supplyequipment 2 into the vacuum chamber 1, a high-frequency power of 13.56MHz is supplied by means of coil-less high-frequency power supplyequipment 4 to a coil 6 provided inside a dielectric cylinder 5 servingas one example of a dielectric window. Thus, plasma is generated in thevacuum chamber 1, allowing the etching on a substrate 8 or a thin filmthereon placed on a substrate electrode 7 to be performed. Further, asubstrate-electrode using a high-frequency power supply 9 for supplyinga high-frequency power of 400 kHz to the substrate electrode 7 isprovided, allowing ion energy reaching the substrate 8 to be controlled.Examples of the thin films on the substrate 8 are a silicon oxide film,a silicon nitride film, etc.

The turbo-molecular pump 3 and an exhaust port 10 are disposed justunder the substrate electrode 7, and a pressure-controlling valve 11 formaintaining the vacuum chamber 1 at the specified pressure is an up-downvalve located just under the substrate electrode 7 and just over theturbo-molecular pump 3. Thus, the pressure-controlling valve 11 moves upand down to control the pressure of the vacuum chamber 1 at thespecified pressure.

A first metal plate 12 is provided at a first-side bottom of thedielectric cylinder 5 facing the substrate electrode 7, and a secondmetal plate 13 is provided at the other (second) side of the dielectriccylinder 5 not facing the substrate electrode 7. The first metal plate12 is connected to the second metal plate 13 by a plurality of bolts 15provided through a space inside the dielectric cylinder 5 and outsidethe vacuum chamber 1, and the dielectric cylinder 5 is fixed by beingsandwiched between the first metal plate 12 and the second metal plate13. That is, as shown in FIG. 5, the dielectric cylinder 5 is located onthe outer edge of the first metal plate 12, and the outer edge of thefirst metal plate 12 and the inner edge of the dielectric cylinder 5 arelocated outside of the inner edge of the second metal plate 13 while thebolts 15 are connected between the first metal plate 13 and the secondmetal plate 12 but not through the dielectric cylinder 5. The bolts 15,the first metal plate 12, and the second metal plate 13 are at theground potential.

Also, as shown in FIG. 5, a line segment interconnecting an arbitrarypoint A on the vacuum-side wall surface of the dielectric cylinder 5 andan arbitrary point B on the substrate surface is interrupted(intersected) by the first metal plate 12 provided at the bottom of thedielectric cylinder 5. That is, when plasma processing is carried out,particles which tend to move straight from a surface of the substrate 8or from a surface of the film on the substrate 8 toward a wall surfaceof the dielectric cylinder 5 inside the vacuum chamber 1 through theplasma processing are interrupted (blocked) by the first metal plate 12,thus preventing deposition of a thin film on the dielectric cylinder 5.

With the etching apparatus having such a constitution, a silicon oxidefilm on a gold film was etched under the conditions of an Ar/CHF₃ of270/30 sccm, a pressure of 2.5 Pa, and an ICP/BIAS of 1500/600 W. Atransition of etching rate is shown in FIG. 6. As apparent from FIG. 6,such declines of etching rate as seen in the prior art example have beeneliminated.

The reason why a stable etching rate has been ensured as explained abovecan be that the gold thin film is no longer deposited on the surface ofthe dielectric cylinder 5, so that the high-frequency electromagneticfield generated in the vacuum chamber 1 as a result of supplying thehigh-frequency power to the coil 6 has become stable in strength.

The above-described embodiments of the present invention show only partof many variations in terms of the configuration of the vacuum chamber,the configuration and placement of the coil and the dielectric cylinderor the like by way of example of the scope of application of the presentinvention. It is needless to say that wide variations in addition to theexamples explained hereinabove are possible in the application of thepresent invention.

Although the above embodiments of the present invention have beendescribed about the etching of an iridium film and the etching of asilicon oxide film formed on a gold film, the present invention isuseful for the etching of a refractory metal film and the etching of athin film formed on a refractory metal film. Among such aspects ofetching, this etching method is useful particularly for cases where therefractory metal film is a film containing at least one element ofiridium, rhodium, ruthenium, platinum, gold, copper, rhenium, bismuth,strontium, barium, zirconium, lead, and niobium.

The above embodiments of the present invention have been described for acase where the first metal plate is provided at a first-side bottom ofthe dielectric cylinder facing the substrate electrode while the secondmetal plate is provided at the other (second) side of the dielectriccylinder not facing the substrate electrode, wherein the first metalplate is connected to the second metal plate by bolts extending throughpenetration holes provided in the dielectric cylinder along the cylinderaxis of the dielectric cylinder while the dielectric cylinder is fixedby being sandwiched between the first and second metal plates, in whichstate the etching is performed. Alternatively, the invention has beendescribed for a case where the first metal plate is provided at afirst-side bottom of the dielectric cylinder facing the substrateelectrode while the second metal plate is provided at the other (second)side of the dielectric cylinder not facing the substrate electrode,wherein the first metal plate is connected to the second metal plate bybolts provided through a space inside the dielectric cylinder while thedielectric cylinder is fixed by being sandwiched between the first andsecond metal plates, in which state the etching is performed. However,various constitutions other than these are possible, of course. Forexample, the first and second metal plates may be connected to eachother by using a metal rod instead of the bolt.

Also, the above embodiments of the present invention have been describedfor a case where the bolt, the first metal plate, and the second metalplate are at the ground potential. Since such a constitution allows thecapacitive coupling between the coil and the plasma to be suppressed,self-biased potential is unlikely to occur to the surface of thedielectric cylinder, offering an advantage that the surface of thedielectric cylinder is less etched. In addition, for prevention ofinductive heating at the bolt or the metal rod, it is desirable that thebolt or the metal rod be coated or plated with a low-resistivity film.

Also, the above embodiments of the present invention have been describedfor a case where a line segment interconnecting an arbitrary point onthe vacuum-side wall surface of the dielectric cylinder and an arbitrarypoint on the substrate surface is interrupted by the first metal plateprovided at the bottom of the dielectric cylinder, in which state theetching is performed. However, this interruption does not necessarilyneed to be perfect, and the design may be given some degree of freedomwithin such a scope as declines of etching rate do not occur.

Also, the above embodiments of the present invention have been describedfor a case where the turbo-molecular pump for exhausting the vacuumchamber is disposed just under the substrate electrode while thepressure-controlling valve for maintaining the vacuum chamber at aspecified pressure is an up-down valve located just under the substrateelectrode and just over the turbo-molecular pump. However, the presentinvention is useful also for cases where the turbo-molecular pump 3 isdisposed at locations other than just under the substrate electrode 7while the pressure-controlling valve 11 is disposed at locations otherthan just under the substrate electrode 7 and comprises a valve otherthan an up-down valve. However, the embodiments of the presentinvention, in which gas exhaust is done isotropically, offer anadvantage that the etching can be achieved uniformly.

Further, although the description has been made for cases where theinternal pressure of the vacuum chamber is 0.3 Pa and 2.5 Pa, the methodof the present invention is useful for cases where the internal pressureof the vacuum chamber is not more than 10 Pa since the lower theinternal pressure of the vacuum chamber is, the larger the part that thephysical etching forms. The method of the present invention is usefulparticularly for cases where the internal pressure of the vacuum chamberis not more than 1 Pa.

Further, although the description has been made for a case where thefrequency of the high-frequency power applied to the coil is 13.56 MHz,the method of the present invention allows high-frequency powers of 100kHz to 100 MHz to be used for the etching at low pressure, thus beinguseful for all of those regions.

Further, although the description has been made for a case where thefrequency of the high-frequency power applied to the substrate electrodeis 400 kHz, the method of the present invention, needless to say, allowsother frequencies, for example, high-frequency powers of 100 kHz to 100MHz to be used for the control of ion energy reaching the substrate.

The dielectric cylinder 5 may be structured longitudinally longer. Inthis case, since the region for high dissociation of plasma occupies anincreased volume, there can be obtained a characteristic that activeparticles of further dissociated composition can be made to act on thesubstrate 8.

In an etching apparatus of a third embodiment of the present invention,a dielectric ring 22 instead of the dielectric cylinder 5 which can beused as a dielectric window is fitted into a hole of a second metalplate 13B so as to locate the dielectric ring 22 as an inner edge of thesecond metal plate 13B. The inner edge of the dielectric ring 22 isbrought into contact with the outer edge of a first metal plate 21 atthe lower side of the dielectric ring 22 while the inner edge of thedielectric ring 22 and the outer edge of the first metal plate 21 aredirectly connected with bolts 15. The coil 6 is provided outside thedielectric ring 22.

In such a construction, as shown in FIG. 11, a line segmentinterconnecting an arbitrary point A on the vacuum-side wall surface ofthe dielectric ring 22 and an arbitrary point B on the substrate surfaceis interrupted by the first metal plate 21 provided on the lower side ofthe dielectric ring 22. That is, when plasma processing is carried out,particles which tend to move straight from a surface of the substrate 8or from a surface of the film on the substrate 8 toward a wall surfaceof the dielectric ring 22 inside the vacuum chamber 1 through the plasmaprocessing can be interrupted (blocked) by the first metal plate 21,thus preventing deposition of a thin film on the dielectric ring 22.Thus, the same effects as the previous embodiments can be obtained inthis third embodiment.

Preferably, the diameter 2R₁ of the first metal plate 12 is 1 to 1.5times larger than the diameter 2R₃ of the substrate electrode 7 and thediameter 2R₂ of the second metal plate 13 is 1.6 to 3 times larger thanthe diameter 2R₃ of the substrate electrode 7. Within such a range, itbecomes possible to form doughnut-shaped high-density plasma in theregion outside the dielectric cylinder 5 or dielectric plate 21, and torealize uniform plasma density in the vicinity of the substrate 8through diffusion. If the diameter 2R₁ of the first metal plate 12 issmaller than the diameter 2R₃ of the substrate electrode 7, a resultantplasma distribution would be convex in the vicinity of the substrate 8.Conversely, if the diameter 2R₁ of the first metal plate 12 is largerthan 1.5 times the diameter 2R₃ of the substrate electrode 7, aresultant plasma distribution would be concave in the vicinity of thesubstrate 8. Further, if the diameter 2R₂ of the second metal plate 13is smaller than 1.6 times the diameter 2R₃ of the substrate electrode 7,enough plasma density could not be obtained in peripheries of thesubstrate 8. Conversely, if the diameter 2R₂ of the second metal plate13 is larger than 3 times the diameter 2R₃ of the substrate electrode 7,excessive plasma density would result in peripheries of the substrate 8.

Preferably, a distance H₁ between the first metal plate 12 and thesubstrate electrode 7 is 40 mm to 150 mm. Within such a range, itbecomes possible to form doughnut-shaped high-density plasma in theregion outside the dielectric cylinder 5 or dielectric plate 21, and torealize uniform, high-density plasma in the vicinity of the substrate 8through diffusion. If the distance H₁ between the first metal plate 12and the substrate electrode 7 is smaller than 40 mm, enough diffusionwould not be done, resulting in concave a plasma distribution in thevicinity of the substrate 8. Conversely, if the distance H₁ between thefirst metal plate 12 and the substrate electrode 7 is larger than 150mm, excessive diffusion of plasma would occur, resulting in a convexplasma distribution in the vicinity of the substrate 8.

Preferably, the distance of the metal rod or the bolt is 10 mm to 50 mm.If the distance between the adjacent metal rods or the adjacent bolts issmaller than 10 mm, the high-frequency electromagnetic field radiatedinto the vacuum chamber by the coil would decline in strength, leadingto a defect that enough plasma density could not be obtained. Also, ifthe distance between the adjacent metal rods or the adjacent bolts islarger than 50 mm, the metal rods or the bolts would decline in thefunction as a faradic shield so that capacitive coupling between thecoil and the plasma would be increased. This is unfavorable in that aself-biased potential would occur to the surface of the dielectriccylinder or plate, causing the surface of the dielectric cylinder orplate to be etched.

When the dielectric cylinder or plate is positioned such that thetransmission plane of the high-frequency electromagnetic field is partlyinterrupted by the metal rod or the bolt, in the transmission plate, theratio of an area of part that is not interrupted by the metal rod or thebolt to the area of the whole dielectric cylinder or plate can bedefined as an aperture. The aperture is preferably not less than 50%. Ifthe aperture is smaller than 50%, the high-frequency electromagneticfield radiated into the vacuum chamber by the coil would decline instrength, leading to a defect that enough plasma density could not beobtained.

The above embodiments of the present invention have been described withrespect to the etching of an iridium film as well as the etching of asilicon oxide film formed on a gold film. However, the present inventionis applicable to general plasma processing for processing a substrate ora film on a substrate. Needless to say, etching can be applied to plasmaCVD and the like. Moreover, the present invention is useful particularlyfor the etching of a refractory metal film and the etching of a thinfilm formed on a refractory metal film. Among such aspects of etching,the method of the present invention is a plasma processing method usefulparticularly for cases where the refractory metal film is a filmcontaining at least one element of iridium, rhodium, ruthenium,platinum, gold, copper, rhenium, bismuth, strontium, barium, zirconium,lead, and niobium.

As apparent from the above description, according to the etching methodof the present invention, while the vacuum chamber is controlled to aspecified internal pressure by exhausting the vacuum chamber andsimultaneously supplying gas into the vacuum chamber, a high-frequencypower of 100 kHz to 100 MHz is applied to a coil provided inside adielectric window such as a dielectric cylinder or plate provided so asto face a substrate placed on a substrate electrode in the vacuumchamber, by which plasma is generated in the vacuum chamber. Thus, aprocess such as etching a substrate or a thin film such as a refractorymetal film on the substrate by the generated plasma can be performedwhile particles which tend to move straight from a surface of thesubstrate or from a surface of the film on the substrate toward a wallsurface of the dielectric window inside the vacuum chamber are keptinterrupted by a metal plate. Thus, a processing operation such as anetching method that allows a stable processing such as etching rate tobe ensured can be realized.

Also, according to the etching method of the present invention, whilethe vacuum chamber is maintained at a specified internal pressure byexhausting the vacuum chamber and simultaneously supplying gas into thevacuum chamber, a high-frequency power of 100 kHz to 100 MHz is appliedto a coil provided inside a dielectric window such as a dielectriccylinder or plate provided so as to face a substrate placed on asubstrate electrode in the vacuum chamber, by which plasma is generatedin the vacuum chamber. Therefore, a process such as etching a thin filmformed on a refractory metal film on the substrate by the generatedplasma can be performed while particles which tend to move straight froma surface of the substrate or from a surface of the film on thesubstrate toward a wall surface of the dielectric window inside thevacuum chamber are kept interrupted by a metal plate. Thus, processingsuch as an etching method that allows a stable processing such asetching rate to be ensured can be realized.

Also, according to the etching apparatus of the present invention, theapparatus comprises a vacuum chamber as well as gas supply equipment forsupplying gas into the vacuum chamber, exhausting equipment forexhausting the vacuum chamber as well as a pressure-controlling valvefor maintaining the vacuum chamber at a specified internal pressure, asubstrate electrode for placing thereon a substrate in the vacuumchamber, a dielectric window such as a dielectric cylinder or plateprovided so as to face the substrate electrode, and a coil providedinside the dielectric window such as a dielectric cylinder or plate aswell as a high-frequency power supply capable of supplying ahigh-frequency power of 100 kHz to 100 MHz to the coil. Thus, processingsuch as an etching apparatus that allows a stable processing such asetching rate to be ensured can be realized.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

1. A plasma processing apparatus, comprising: a vacuum chamber; gassupply equipment for supplying gas into the vacuum chamber; an exhaustequipment for exhausting the vacuum chamber; a pressure-controllingvalve for controlling the internal pressure of said vacuum chamber; asubstrate electrode for receiving thereon a substrate in the vacuumchamber; a dielectric cylinder having openings at both ends thereof andarranged such that one of the openings faces the substrate electrode; acoil provided inside the dielectric cylinder and outside the vacuumchamber; high-frequency power supply equipment capable of supplyinghigh-frequency power of 100 kHz to 100 MHz to the coil; a first metalplate provided at the one of the openings of the dielectric cylinder,the one of the openings being on a side of the dielectric cylindercloser to the substrate electrode and being closed by the first metalplate; and a second metal plate provided at a peripheral edge of theother of the openings of the dielectric cylinder, wherein the firstmetal plate is connected to the second metal plate by a metal rod or abolt extending through a penetration hole provided in the direction of acylinder axis of the dielectric cylinder, the dielectric cylinder beingfixed by being sandwiched between the first metal plate and the secondmetal plate.
 2. A plasma processing apparatus according to claim 1,wherein the metal rod or bolt, the first metal plate, and the secondmetal plate are at a ground potential.
 3. A plasma processing apparatusaccording to claim 1, wherein a line segment interconnecting anarbitrary point on a vacuum-side wall surface of the dielectric cylinderand an arbitrary point on a surface of the substrate is interrupted bythe first metal plate provided at the bottom of the dielectric cylinder.4. A plasma processing apparatus according to claim 1, wherein adiameter of the first metal plate is 1 to 1.5 times a diameter of thesubstrate electrode and a diameter of the second metal plate is 1.6 to 3times a diameter of the substrate electrode.
 5. A plasma processingapparatus according to claim 1, wherein a distance between the firstmetal plate and the substrate electrode is 40 mm to 150 mm.
 6. A plasmaprocessing apparatus, comprising: a vacuum chamber; gas supply equipmentfor supplying gas into the vacuum chamber; exhaust equipment forexhausting the vacuum chamber; a pressure-controlling valve forcontrolling the internal pressure of said vacuum chamber; a substrateelectrode for receiving thereon a substrate in the vacuum chamber; adielectric cylinder having openings at both ends thereof and arrangedsuch that one of the openings faces the substrate electrode; a coilprovided inside the dielectric cylinder and outside the vacuum chamber;high-frequency power supply equipment capable of supplyinghigh-frequency power of 100 kHz to 100 MHz to the coil; a first metalplate provided at the one of the openings of the dielectric cylinder,the one of the openings being on a side of the dielectric cylindercloser to the substrate electrode and being closed by the first metalplate; and a second metal plate provided at a peripheral edge of theother of the openings of the dielectric cylinder, wherein the firstmetal plate is connected to the second metal plate by a metal rod or abolt provided through a space inside the dielectric cylinder, thedielectric cylinder being fixed by being sandwiched between the firstmetal plate and the second metal plate.
 7. A plasma processing apparatusaccording to claim 6, wherein the metal rod or bolt, the first metalplate, and the second metal plate are at a ground potential.
 8. A plasmaprocessing apparatus according to claim 6, wherein a line segmentinterconnecting an arbitrary point on a vacuum-side wall surface of thedielectric cylinder and an arbitrary point on a surface of the substrateis interrupted by the first metal plate provided at the bottom of thedielectric cylinder.
 9. A plasma processing apparatus according to claim6, wherein a diameter of the first metal plate is 1 to 1.5 times adiameter of the substrate electrode and a diameter of the second metalplate is 1.6 to 3 times a diameter of the substrate electrode.
 10. Aplasma processing apparatus according to claim 6, wherein a distancebetween the first metal plate and the substrate electrode is 40 mm to150 mm.